I like transformers

[The Electrician]

I'm a retired EE living in the PNW. When I had to work for a living, I designed a lot of power (iron and ferrite cored) transformers, but no audio transformers. Since I retired I can analyze whatever I want. I have become interested in researching the work on audio transformers that was done at Bell Telephone Laboratories over a hundred years ago. The improvements in audio transformers and audio inductors those engineers made during the first half of the 20th century is amazing.

As a result of having been involved with some startup companies, I have come into possession of a fair amount of test equipment. In particular my need to measure transformers has left me with several high-end LCR/Impedance analyzer meters and I'll show some interesting measurements.

I don't have a lot of high-end audio equipment, but I have a friend who has been a Pro audio engineer, and he has a lot of audio transformers which I borrow from him to make measurements. I have also bought some items just make measurements.

 

[user 137017]

hello from Aintree, uk. im sure you will have many here picking your brain. myself included.

 

[andYz00m]

Welcome!

You can take a look in the magnetics section for all the fun docs and discussions around transformers. Lots of experienced folks here.

 

[ruffrecords]

It is good to have another magnetics expert on board. Welcome.

Cheers

Ian

 

[L´Andratté]

Welcome!
Transformers put a spell on another poor soul...

 

[gyraf]

Welcome! We sure have some interests in common...

/Jakob E.

 

[terry setter]

I'm a retired EE living in the PNW. When I had to work for a living, I designed a lot of power (iron and ferrite cored) The improvements in audio transformers and audio inductors those engineers made during the first half of the 20th century is amazing... I don't have a lot of high-end audio equipment, but I have a friend who has been a Pro audio engineer, and he has a lot of audio transformers which I borrow from him to make measurements. I have also bought some items just make measurements.

Warning in advance (please take this kindly, as that is how I intend it). Some of the "best" audio transformers don't test as "good" as ones that are less sonically interesting. Or, they test well in some aspects and not-so-well in others. This makes our work as designers FAR more complex as measurements do not tell the full story. Only ears - and the resulting layers of personal opinions - finally determine which transformers are good sounding, and in which circuits they sound good (ah, more trouble!). For example, Lundahl makes a dandy microphone output transformer (LL1940). Dandy in that it measures well, but I find it to be to be uninteresting: "dull as dishwater". However, some of the mic output transformers that have significant resonances within the audio spectrum, or distort badly at low frequencies sound very good to me, like the AMI T14. Here are some screen shots to have fun with.

You'll see that the Lundahl that I consider to be boring is very good at 20HZ and even at 15HZ! Whereas, the AMIT-14, the sonics of which are highly regarded by many, has stronger resonance at 10KHZ (though with less overshoot, so there's discussion to be had here), but it is starting to show distortion at 30HZ, and is bad at 25HZ, and worse still at 20HZ.

I threw in one that I call Chinese Junk, which sounds awful to my ears, though at 10KHZ, it doesn't look too much worse than some respected mic output transformers. You'll see that is has started to go noticeably south at 40HZ, is lousy at 30HZ, and an affront to all humankind at 20HZ.

The final shots are of a Cinemag 2461 NiCo, which is my favorite sounding of the lot. It also has the most massive core.

 

[ruffrecords]

Warning in advance (please take this kinrdly, as that is how I intend it). Some of the "best" audio transformers don't test as "good" as ones that are less sonically interesting.

Unfortunately "sonically interesting" is in the ear of the beholder and not something the can be definitively parameterised. I design tube mixers with transformers at the inputs and outputs and aim as far as possible for a transparent signal path. Yet I get lots of people asking, will this tube sound better or can I use this transformer because I like the way it sounds? I cannot answer these questions because what sounds good to me may not sound good to anyone else. Such discussions are therefore pointless.

What is worth discussing is the limitations of practical transformers and and how they affect the signal passing through them.

Cheers

Ian

 

[Newmarket]

Warning in advance (please take this kindly, as that is how I intend it). Some of the "best" audio transformers don't test as "good" as ones that are less sonically interesting. Or, they test well in some aspects and not-so-well in others. This makes our work as designers FAR more complex as measurements do not tell the full story. Only ears - and the resulting layers of personal opinions - finally determine which transformers are good sounding, and in which circuits they sound good (ah, more trouble!). For example, Lundahl makes a dandy microphone output transformer (LL1940). Dandy in that it measures well, but I find it to be to be uninteresting: "dull as dishwater". However, some of the mic output transformers that have significant resonances within the audio spectrum, or distort badly at low frequencies sound very good to me, like the AMI T14. Here are some screen shots to have fun with.

You'll see that the Lundahl that I consider to be boring is very good at 20HZ and even at 15HZ! Whereas, the AMIT-14, the sonics of which are highly regarded by many, has stronger resonance at 10KHZ (though with less overshoot, so there's discussion to be had here), but it is starting to show distortion at 30HZ, and is bad at 25HZ, and worse still at 20HZ.

I threw in one that I call Chinese Junk, which sounds awful to my ears, though at 10KHZ, it doesn't look too much worse than some respected mic output transformers. You'll see that is has started to go noticeably south at 40HZ, is lousy at 30HZ, and an affront to all humankind at 20HZ.

The final shots are of a Cinemag 2461 NiCo, which is my favorite sounding of the lot. It also has the most massive core.

But not everyone is not looking for a particular "sound" from a transformer. In many cases they would simply wish it to be as transparent as possible whilst performing the basic task of galvanic isolation and (with the exception of 1:1 transformers) impedance / level change.

 

[cfanzalone]

I think I've said this before...Transformers are most important...But what do you want out of a transformer??? Do you want a particular flavor?? Like the above poster...sure each brand has it's own character (sound) that it imparts.
My experience comes from tube mics and tube/SS preamps. I have tried every brand under the sun. I like clean character...to do it's job with a minimal of it's own sonic identities/anomalies...
In mics, both tube and FET, I have always chosen Cinemag as the stellar "musical" transformer...I have personal experience with comparisons. In agreement with the former poster. In preamps, sure I've tried the ""Get this, put this it in"...why??? for "flavor of the month for status or resale"?? ...It rarely works...
I agree again with the former poster...IF you have money, buy and try them all...your ear WILL tell the difference depending what you want....
BTW, I am no way affiliated with any transformer manufacturers:...AMI/Cinemag/Lundhal/Edcor,/Jensen etc...I've tried them and I trust my ears...

Best regards

 

[terry setter]

Yes Roughrecords and Newarket, I agree with both of you. My post is only intended to "warn" The Electrician that these are exactly the kinds of unresolvable, beauty-is-in-the-ear-of-the-beholder issues that he will encounter when getting involved with transformer design and implementation - not that that has stopped any of us!

 

[john12ax7]

I've never heard a truly transparent transformer. Imo their character is part of the fun.

 

[Matt Syson]

What is usually ignored is that every transformer will give a different 'response' depending on EXACTLY the source impedance, reactance,level feeding into it AND then the 'load' on the secondary which itself impacts on how the transformer AND the source impedance react. Couple this with the obvious subjective observations by (probably) biased 'audience' (the person who is listening) and through a chain of random amplifiers and speakers it is impossible to say how any transformer will actually 'sound'. The east things to measure like frequency response and distortion are BOTH dependent on signal level and the source/load impedances (especially if reactive). Hence they are tested using sources and loads that are as near resistive because using a reacive source/load makes repeatable results that can then relate to anything else impossible.

 

[MisterCMRR]

As previous posters have stated, a truly well-designed audio transformer can be extremely faithful, transparent, uncolored, etc. provided it is used in circuits that it was designed for. Some who audition them don't seem to understand that there is no "universal" transformer. Some don't even understand the fundamental differences between input and output transformers! IMHO, Jensen designs are about as good as it gets. I know of no other manufacturer obsessed with things like time-domain distortions (accurately described as deviations from linear phase or DLP). To achieve transparency in the time domain requires Bessel-contoured HF roll-off, and at least a decade of extended LF response (down to 2 Hz or less). Typical DLP is ±2° across 20 Hz to 20 kHz for a Jensen. Many times customers will report an "amazing new mid-range clarity" which we know comes from the Bessel HF roll-off. It removes ultrasonic garbage from the signal - which prevents discordant non-harmonic distortion in downstream amplification. "DC to daylight" design philosophy always opens the door for subtle but ugly distortion products! And I categorically refuse to modify good designs to satisfy a "distortion of the day" trend!

Bill Whitlock
AES Life Fellow
Chino, CA, USA

 

[The Electrician]

I'm a retired EE living in the PNW. When I had to work for a living, I designed a lot of power (iron and ferrite cored) transformers, but no audio transformers. Since I retired I can analyze whatever I want. I have become interested in researching the work on audio transformers that was done at Bell Telephone Laboratories over a hundred years ago. The improvements in audio transformers and audio inductors those engineers made during the first half of the 20th century is amazing.

As a result of having been involved with some startup companies, I have come into possession of a fair amount of test equipment. In particular my need to measure transformers has left me with several high-end LCR/Impedance analyzer meters and I'll show some interesting measurements.

I don't have a lot of high-end audio equipment, but I have a friend who has been a Pro audio engineer, and he has a lot of audio transformers which I borrow from him to make measurements. I have also bought some items just make measurements.

I haven't posted anything since this intro post because shortly after this, I caught covid19, which I had avoided for 3 years. This is not a good life event for old, retired people.
But, I'm back to a good approximation of normal.

 

[Ricardus]

But, I'm back to a good approximation of normal.

That's good. Be well.

 

[ruffrecords]

I haven't posted anything since this intro post because shortly after this, I caught covid19, which I had avoided for 3 years. This is not a good life event for old, retired people.
But, I'm back to a good approximation of normal.

Apparently, the version going round now is a lot worse than the original. I am in my 70s and have so far avoided it but my 45 year old daughter recently got it and it floored her. I am very pleased to hear you made it though OK.

Cheers

ian

 

[Newmarket]

Best wishes and good thoughts.
And a useful reminder that Covid-19 doesn't go away when lockdowns etc. are lifted.